• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1844-1846
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• 2005

The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR property of self-assembled 4,4- Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto pre-treatment$(H_2SO_4:H_2O_2=3:1)$ Si. The Au substrate was exposed to a 1mM/l solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a $0.1{\mu}M/l$ solution of 4,4-Di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2$, and finally blown dry with $N_2$. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2V to +2V with 299K temperature. The vacuum condition is $6{\times}10^{-8}$ Torr. As a result, we found the NDR voltage of the nitro-benzene is $-1.61{\pm}0.26$ V(negative region) and $1.84{\pm}0.33$ (positive region), respectively.

• Journal of Pharmaceutical Investigation
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• v.38 no.2
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• pp.119-126
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• 2008

Solid dispersions of poorly water-soluble drug, sibutramine, were prepared with hydrophilic polymer, poly-N-vinylpyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC) and organic acid, citric acid, to improve the solubility of drug. Physicochemical variation and shape of microsphere were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC) and Fourier-transform infrared spectroscopy (FT-IR). Microspheres containing additives showed more spherical shape than non additive microspheres. In vitro release behavior of microspheres presented at simulated gastric fluid (pH 1.2) and simulated intestinal fluid (pH 6.8). The solid dispersion form transformed the drug into an amorphous state and dramatically improved its dissolution rate. These data suggest that the solid dispersion technique is an effective approach for developing the appetite depressant drug products and various pharmaceutical excipients are able to control the release behaviors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.489-494
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• 2004

In this paper, we investigated impurities content and thermal properties showing by changing the content of carbon black which is semiconductive materials for underground power transmission. Specimens were made of sheet form with the three of existing resins and the nine of specimens for measurement. Impurities content of specimens was measured by ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer), and density of specimens were measured by density meter. And then heat capacity(${\Delta}H$) and melting temperature(Tm), specific heat(Cp) were measured by DSC(Differential Scanning Calorimetry). The dimension of measurement temperature was $0[^{\circ}C]\;to\;200[^{\circ}C]$, and rising temperature was $4[^{\circ}C/min]$. Impurities content was highly measured according to increasing the content of carbon black from this experimental result also density was increased according to these properties. Specially, impurities content values of the A1 and A2 of existing resins were measured more than 4000[ppm]. Heat capacity, melting temperature, and specific heat from the DSC results were simultaneously decreased according to increasing the content of carbon black. Because metallic impurities of carbon black having Fe, Co, Mn, A1 and Zn are rapidly passed kinetic energy increasing the number of times breaking during the unit time with the near particles according to increasing vibration of particles by the applied heat energy.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.513-520
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• 2006

The effect of chlorination on disinfection byproducts (DBPs) production from bloom-forming freshwater algae including 7 strains of cyanobacteria and 6 strains of diatoms was investigated. The release and degradation of hepatotoxin (microcystins) by the chlorination on Microcystis under differential condition of the chlorination time and dose were also investigated. The disinfection byproducts formation potentials (DBPFP) of cyanobacterial species and diatoms were ranged from 0.017 to $0.070{\mu}mol\;DBPs/mg$ C and from 0.129 to $0.708{\mu}mol\;DBPs/mg$ C respectively. Among three major groups of DBPs, haloacetonitrils (HANs) was major product in most test strains except Aphanizomenon sp. and Oscillatoria sp. Haloacetic acids (HAAs) was less than 5 % of total DBPs. Chloroform and dichloroacetonitril (DCAN) were dominant compounds in trihalomethanes (THMs) and HANs respectively. After 4 hours chlorination of toxic Microcystis aeruginosa under the dose range of 0.5 to $10mg\;Cl_2/L$, the concentration of intracellular microcystins decreased, but dissolved dissolved microcystins concentration increased with the treatment of more than $3mg\;Cl_2/L$. However the total amount of microcystins was almost constant even at $10mg\;Cl_2/L$ of chlorination. To conclude, our results indicate that the chlorination causes algal cell lysis and release of intracellular microcystins in the intact form to surrounding waters.

• Korean Journal of Head & Neck Oncology
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• v.24 no.1
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• pp.53-56
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• 2008

Objectives：The purpose of this study was to evaluate the variable sonographic features in addition to classic findings and to find the helpful characteristic findings for diagnosis of branchial cleft cysts. Subjects and Methods：We retrospectively analyzed the sonographic finding of 16 histopathologically proven branchial cleft cysts. Assessment involved the following variables : location related to carotid artery, size, cyst wall, border, margin, shape, internal echotexture, post echoic enhancement, orientation of longitudinal axis relative to the long axis of the neck, and tapering edge. Results：Most branchial cleft cysts were seen as well defined(15/16), oval shape(13/16), smooth inner (12/16) and outer margin(13/16), and post echoic enhancement(16/16). Their diameter varied from 1 to 6cm (mean 3.3cm). The branchial cleft cysts showed variable internal echopatterns；hyperechogenicity or pseudosolid appearance(1/16), heterogeneous echogenicity(4/16) in addition to classic form of anechoic(5/16) or hypoechoic internal echogenicity(6/16). Longitudinal axis of most branchial cleft cysts were arranged in the direction of the long axis of the neck(13/16) and some branchial cleft cysts had tapering edge(6/16). Conclusion：If both atypical sonographic findings and location are showed, longitudinal arrangement of long axis and tapering edge of branchial cleft cysts are helpful findings for differential diagnosis.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.17 no.2
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• pp.59-63
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• 1981

For the purpose of surveying accuracy of the position fix and local fluctuation of Omega signals in south coast of Korea, the author observe continuously the phase difference of the A-C pair and A-E pair form December 1, 1980, to February 28, 1981, at Cheju(33$^{\circ}$31'.0N, 126$^{\circ}$31.9E) and Busan(35$^{\circ}$7'.9 N, 129$^{\circ}$6'. 3 E). The analyzed results are as follows: 1. Omega signals at Cheju and Busan are positive correlation. Mean value of coefficients during all measured time is 0.70 with A-C pair and 0.75 with A-E pair. 2. Range of mean value of difference between the measured PPC at Cheju and Busan is 17.7~21.3 cels with A-C pair and -2.9~2.0 cels with A-E pair. 3. In case of using the differential Omega at Cheju and Busan, mean value of total errors of the position fix is 1.52 miles and its standard deviation is 0.21 miles.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.4
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• pp.101-115
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• 2020

It is very important for companies to form a strong brand resonance to maximize profits, attract new customers, and prevent them from leaving existing customers. In this study, we examined the relationship between brand awareness factors and brand attachment leading to brand identity cognition, brand performance, and brand emotion, and verified how brand attachment plays a role in shaping brand resonance. As a result, it was confirmed that brand emotion among brand awareness factors is a key factor affecting brand attachment and forming brand resonance. In addition, if the perception of brand identity is established until the true brand resonance of consumers is established, they will experience the true value of the brand through differential performance on the brand, and further increase the emotional response of consumers. This led to deep solidarity with the brand and consumers through attachment to the brand, interacting with the brand and showing high brand empathy behavior.

• Journal of Korean Neurosurgical Society
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• v.55 no.4
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• pp.226-229
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• 2014

We describe a rare case of intradural-extramedullary primary spinal cysticercosis. A 42-year-old man visited our institute for lower back pain. He denied having consumed raw meet. Magnetic resonance (MR) images revealed an intradural pure cystic mass at the L3-L4 level. A radiologic diagnosis of spinal arachnoid cyst was established. Three years later, he complained of aggravated back pain, and follow-up MR examination showed a markedly expanded cyst, occupying the subarachnoid space from the T11 to the S1 level. L2 hemilaminectomy was performed, and a yellowish infected cyst bulged out through the dural opening. The cyst was removed en bloc. The histopathological findings of the cyst were consistent with parasitic infection. Serum enzyme-linked immunosorbent assay (ELISA) confirmed the presence of spinal cysticercosis. As there was no intracranial lesion, the final diagnosis was primary spinal cysticercosis, which is very rare. MR imaging is a sensitive diagnostic tool for detecting cystic lesions in the spine; however, it is difficult to distinguish cysticercosis from non-infectious cysts such as an arachnoid cyst without using gadolinium enhancement. Clinicians treating spinal cysts with an unusual clinical course should include cysticercosis as a differential diagnosis. We recommend contrast-enhanced MR imaging and serum ELISA in the diagnostic work-up of such cases.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.365-380
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• 2020

The focus of this paper is to develop an analytical approach based on an efficient shear deformation theory with stretching effect for bending stress analysis of cross-ply laminated composite plates subjected to transverse parabolic load and line load by using a new kinematic model, in which the axial displacements involve an undetermined integral component in order to reduce the number of unknowns and a sinusoidal function in terms of the thickness coordinate to include the effect of transverse shear deformation. The present theory contains only five unknowns and satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without using any shear correction factors. The governing differential equations and its boundary conditions are derived by employing the static version of principle of virtual work. Closed-form solutions for simply supported cross-ply laminated plates are obtained applying Navier's solution technique, and the numerical case studies are compared with the theoretical results to verify the utility of the proposed model. Lastly, it can be seen that the present outlined theory is more accurate and useful than some higher-order shear deformation theories developed previously to study the static flexure of laminated composite plates.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.97-104
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• 2005

A simple but efficient grid generation technique by using the modified compressible form of stream function has been formulated. Transformation of a physical plane to a streamline plane, the Von Mises Transformation, has been widely used to solve the differential equations governing flow phenomena, however, limitation arises in low velocity region of boundary layer, mixing layer and wake region where the relatively large grid spacing is inevitable. Modified Von Mises Transformation with simple mathematical adjustment for the stream function is suggested and applied to solve the confined coaxial turbulent jet mixing with simple $\kappa-\epsilon$ turbulence model. Comparison with several experimental data of axial mean velocity, turbulent kinetic energy, and Reynolds shear stress distribution shows quite good agreement in the mixing layer except in the centerline where the turbulent kinetic energy distributions were somewhat under estimated. This formulation is strongly suggested to be utilized specially for free turbulent mixing layers in axisymmetric flow conditions such as the investigation of mixing behavior, jet noise production and reduction for Turbofan engines.